This invention relates to a disc cartridge having a disc-shaped recording medium, such as an optical disc or a magneto-optical disc, rotatably housed within a main cartridge body.
There has hitherto been proposed a recording disc for recording desired information signals, such as an optical disc or a magneto-optical disc. Such recording disc is usually handled as a disc cartridge in which the disc is accommodated within a main cartridge body in order to facilitate handling or to prohibit dust and dirt from becoming attached to the recording medium.
Such known disc cartridge has a main cartridge body 103 formed by abutting an upper cartridge half 101 and a lower cartridge half 102 to each other and a recording disc 104 rotatably accommodated in the main cartridge body, as shown in FIGS. 1 and 2.
There is formed in the main cartridge body 103 a rectangular-shaped aperture 105 for recording/reproduction of signals on the disc 104 by means of an optical unit or a magnetic head having access thereto through the aperture 105. This aperture 105 extends in a direction perpendicular to the cartridge inserting direction indicated by arrow Y in FIG. 1 and may be opened or closed by a shutter 106 formed e.g., from a metal sheet or the like. The aperture 105 remains closed except during recording/reproduction. The shutter 106 is opened by a shutter opening member provided in the recording/reproducing apparatus. The techniques pertinent thereto were proposed by the present Assignee in two US patent publications which matured as U.S. Pat. Nos. 5,272,693 and 5,367,422.
The size of the disc cartridge is determined not only by the size of the recording disc 104 but also by the size of the shutter 106 and the size of the aperture 105 which in turn are determined by the range of movement of an optical pickup 107 enclosed within the recording/reproducing apparatus between the inner most position X1 on the disc 104 and the outer most position X2 on the disc). That is, the size of the disc cartridge is determined by the size of the aperture 105 and the arrangement of the shutter 106. For example, in the case of the recording disc 104 with a diameter of 120 mm, the disc cartridge has a width W1 of 130 mm and a width W2 of 135 mm in the disc inserting direction and in the direction perpendicular thereto, respectively.
Once the size of the disc cartridge is determined, the size of the recording/reproducing apparatus accommodating the disc cartridge is determined unequivocally therefrom. Thus the recording/reproducing apparatus may be reduced in size by reducing the size of the disc cartridge.
Although the disc cartridge may be reduced in size by arranging part of the optical pickup 107 outside of the main cartridge body 103, the recording/reproducing apparatus itself is unchanged in size and cannot be reduced in size. For reducing the size of the disc cartridge, it is necessary to attempt this in connection with the recording/reproducing apparatus.
The disc cartridge is provided with a mistaken insertion prohibiting mechanism for prohibiting insertion of the disc cartridge into the recording/reproducing apparatus in case it is attempted to introduce the disc cartridge in a mistaken direction into the recording/reproducing apparatus. Such a mistaken insertion prohibiting mechanism has been proposed in which a mistaken insertion prohibitive member adapted for being engaged in one or more grooves formed in the side wall or the bottom plate of the main cartridge body is provided in the recording/reproducing apparatus.
However, if the groove(s) for prohibiting mistaken insertion is provided in the main cartridge body, a redundant space is required for providing the groove(s). Above all, in a disc cartridge required to be reduced in thickness, limitations are placed on the width or depth of the groove(s) that can be provided thus imposing strict mounting precision on mistaken insertion prohibiting components provided in the recording/reproducing apparatus. The disc cartridge tends to be poor in strength and hence cannot withstand a large external force. In addition, provision of the groove(s) occasionally leads to surface irregularities giving rise to collision with the recording/reproducing apparatus or with the disc cartridge being introduced into the apparatus.
On the other hand, the disc cartridge needs to be loaded at a pre-set loading position in the recording/reproducing apparatus in connection with the facing distance or relative disposition between the recording disc on one hand and the optical pickup or the magnetic head on the other hand.
To this end, the disc cartridge has cartridge positioning holes for receiving a pair of positioning pins provided in the recording/reproducing apparatus. The positioning pins are engaged in the cartridge positioning holes for setting the fore-and-aft and left-and-right position of the disc cartridge and the height level of the disc cartridge with respect to the recording/reproducing apparatus.
However, as for the reference for the height level, there is no structural difference between actual disc cartridges, although the area in which to provide the cartridge positioning hole is prescribed in the design standards. This results in limitations imposed on surface finishing inclusive of that for a positioning portion, such as satin finishing, thus rendering it difficult to perform slip-proof knurling of a portion gripped by the user.
Furthermore, the height level at which the disc cartridge is secured is also influenced by fluctuations in the outer size of the positioning pins provided in the recording/reproducing apparatus. For example, if the positioning pins are of larger or smaller diameters due to the fluctuations in the machining precision, the height level of the disc cartridge with respect to the recording/reproducing apparatus may be varied due to difference in the contact area between the height setting pins and the disc cartridge.